Amplifiers are classified based on certain operating characteristics. Class-D amplifiers, in contrast to Class-A, Class-B, or Class-AB amplifiers, use the switching modes of transistors to regulate power delivery. Class-D amplifiers are preferred for many applications because the full “on” or full “off” characteristic of the gating signals ensures that the driver portion of the circuit is very power efficient. A Class-D amplifier is often used as a low frequency amplifier due to the high efficiency and low heat dissipation characteristics. An example low frequency amplifier application is an audio amplifier.
In some applications, analog-input Class-D amplifiers are used; however, they require high precision analog components and generally require complicated analog control. However, analog components that are required in some analog-input Class-D amplifier applications, such as the analog integrators and the ramp generators therein, are difficult to be reliably fabricated with sufficient precision in some present day semiconductor manufacturing processes.